Two-stage Pulse Tube Cryocooler Research Articles

Numerical investigation on non-linear streaming effects in a two-stage coaxial pulse tube cryocooler

Stirling pulse tube cryocoolers (PTC) are widely used in aerospace applications for the cooling of infrared sensors and for filtering background thermal noise in the astro-imaging devices, etc. Present investigation aims to use numerical methods to demonstrate the nonlinear fluid flow, heat transfer, and vortex generation phenomena in a two-stage coaxial type inertance pulse tube cryocooler. The numerical simulation is conducted using commercially available Fluent® code for both single-stage and multi-stage configurations to show nonlinear processes with varying heat load conditions. It has been noticed that the width of the vortex produced inside the pulse tube grows with an increase in heat load capacity. This undesirable flow conditions yields an adverse effect in the cooling behavior and reduces overall performance of cryocooler with higher heat load. Additionally, streamlines, stream function, pressure and temperature variation plots are given for both stages with different heat load capacity to substantiate our results.

Optimization of the Swept Volume Ratio between the Compressor and the Active Displacer in an Efficient 20 K Thermal-Coupled Two-Stage Pulse Tube Cryocooler

Optimization of the Swept Volume Ratio between the Compressor and the Active Displacer in an Efficient 20 K Thermal-Coupled Two-Stage Pulse Tube Cryocooler

High-frequency two-stage gas-bearing pulse tube cryocoolers at 20 K for space applications

Gas-bearing pulse tube cryocoolers (PTCs) are efficient and durable for the elimination of supporting and reciprocating parts of the compressor components. Compared with the leaf-spring-suspension compressors, the PTCs with the characteristics of high efficiency, lightweight, compactness, and considerable temperature regulation of PTCs have arousedwideconcern but were rarely investigated. Here, we report the regenerative packing sections of two-stage PTCs under harsh working conditions (i.e., the hot-end temperatures of the compressor and cold finger were 333 K and 313 K, respectively), and the dimensions of pulse tubes (1st and 2nd) were systematically explored. The heat functional (sub)structures and obtained compressor curves coupling with the cold fingers showed an excellent cooling capacity of 0.05 W@20 K at the heat rejection temperature of 293 K. The operating frequency is 52 Hz, which is far beyond the typical high-frequency 40 Hz; and the input electric power is 450 W. Gas-bearing PTCs can meet the requirements of space telescopes for 20 K temperature regions. This study makes a difference in promoting the application of gas-bearing PTCs in cryogenic cooling and remote sensing for aerospace applications, which also provides a feasible way to realize the lightweight of space cryocoolers with considerable efficiency, high reliability, and durable lifespan.

4 K GM-type pulse tube cryocooler with large cooling capacity

Owing to the advantages of large cooling capacity, low vibration and high reliability, GM-type pulse tube cryocoolers at liquid helium temperature have important applications in frontier fields of condensed matter physics research, quantum computing, etc. The phase shifter has an important influence on the cooling performance of pulse tube cryocooler. Previous researches on the phase shifter of GM-type pulse tube cryocooler mainly focused on the effect of a single phase shifter on the performance of the cryocooler at liquid helium temperature. In this paper, based on Sage software, a simulation model of a 4 K two-stage gas-coupled GM-type pulse tube cryocooler is first designed and constructed. The influence of the phase shifters of the two stages on the first-stage and the second-stage temperatures are calculated. The adjustment and optimization process of the cryocooler to obtain the liquid helium temperature is studied. Numerical simulations are given below. 1) The lowest temperature of the model is only about 100 K when the phase shifters of the two stages are closed. The lowest temperature of the model can be reduced to 2.7 K by optimizing the first-stage orifice valve, the second-stage orifice valve, the first-stage double-inlet valve and the second-stage double-inlet valve in sequence. 2) The first-stage orifice valve, the second-stage orifice valve, and the second-stage double-inlet valve have a significant effect on reducing the cooling temperature of the second stage, while the first-stage double-inlet valve has little effect on reducing the temperature of the second stage. 3) The first-stage orifice valve and the second-stage double-inlet valve have a significant effect on reducing the cooling temperature of the first stage, and the first-stage double-inlet valve has little effect on reducing the temperature of the first stage. The second-stage orifice valve will worsen the first stage performance. Finally, an experimental system is constructed. The lowest temperature of the experimental prototype can reach 3.1 K, and the cooling capacity of 0.8 W can be produced at 4.2 K, which is presently the best result obtained by the domestic two-stage gas-coupled valve-separated GM type pulse tube cryocooler. This research can not only promote the independent construction of domestic 4 K refrigeration platform, but also support the relevant frontier basic scientific research and the development of important scientific instruments and equipment. In the future, the structure of the first-stage cold-end heat exchanger and the impedance matching between the compressor and the cryocooler will be improved, and the gas coupling characteristics inside the cryocooler will be studied theoretically and experimentally in depth.

Influence of frequency and pressure on entropy production characteristics of regenerator at 20 K pulse tube cryocooler

Highly sensitive very long band infrared detectors present the need for 2-stage pulse tube cryocoolers in the 20 K temperature region. The entropy production is closely related to the operating frequency and operating pressure of the cryocoolers, which limits the performance of cryocoolers. The entropy production characteristics with operating frequency at 35∼45 Hz and the operating pressure at 2.4∼3.2 MPa of a two-stage pulse tube cryocooler working at 20 K are studied. Active phase regulation is used to reduce the effect of impedance caused by pressure and frequency in the regenerator. The entropy production characteristics, acoustic power, and axial distribution of energy flow of the cold finger at different operating frequencies and operating pressures are compared theoretically. The results show that at a constant input acoustic power and an operating pressure of 2.8 MPa, the cooling capacity increases and the pre-cooling capacity decreases as the operating frequency decreases. At the operating frequency of 40 Hz, the secondary cooling capacity and the required pre-cooling capacity increased with the increase of operating pressure. Further, an experimental test platform is built to verify the simulation. Experimental phenomena are analyzed and interpreted in terms of the average temperature and impedance characteristics along the axial of the finger. This study provides a reference for the optimization of the entropy production and performance improvement of the regenerator of pulse tube cryocooler, especially the thermally coupled pulse tubes cryocooler working at the liquid hydrogen temperature for high-sensitivity infrared detection.

Development of a 2∼4 K closed-cycle JT cryocooler for space application

Cryogenic system proving cooling capacity at liquid helium temperatures is one of the key technologies for space exploration missions. A closed-cycle Joule-Thomson cryocooler capacity of providing different cooling powers at 2∼4 K is developed in our lab. The cryocooler is precooled by a two-stage thermal coupled pulse-tube cryocooler with active phase shifter and driven by multi-stage valved linear compressors. The lowest temperature about 2.5 K and more than 50 mW at about 4.0 K can be obtained by adapting the suited charging pressures. The two-stage pulse tube cryocooler can provide pre-cooling capacity at 17 K and 76 K, respectively with an input power of about 350 W. A large pressure ratio of about 26 and a mass flow rate of 6.7 mg/s can be provide by the multi-stage valved linear compressors with a charge pressure of 0.6 MPa and a total electrical power of less than 110 W. The cooling-down time for the cryocooler from room temperature to about 4 K is less than 10 hours. The cooling system can provide a required cryogenic environment for future space applications.

Development of a 20K two-stage Stirling type pulse tube cryocooler with pre-cooling inside second-stage pulse tube

Cryocoolers working in the liquid hydrogen temperature are important for applications such as cryo-pump, superconductor cooling and cryogenic electronics. This paper analyzes and compares the 20K gas-coupled two-stage Stirling type pulse tube cryocooler with and without pre-cooling. The pre-cooling uses some of the cooling power generated by the first stage cold head to pre-cool the middle of the second stage pulse tube. Given the same input acoustic power, the simulation results show that the cooling capacity of the second stage increase from 0.64 W to 2 W@20 K while the first stage available cooling capacity decrease from 5.84 W to 3 W@77 K when the pre-cooling is used. Meanwhile, the cryocooler relative Carnot Efficiency in terms of acoustic power increases from 10.3% to 14.6%.

Performance testing and temperature fluctuations of a 4.5 K@150 mW Joule-Thomson closed cycle cryocooler for space applications

To meet future space applications, the Shanghai Institute of Technology Physics, Chinese Academy of Sciences (SITP, CAS) has developed a closed cycle Joule-Thomson (JT) cryocooler with a prospect of providing more than hundred milliwatts at liquid helium temperatures. The JT cryocooler is driven by staged efficient valved linear compressors with a pressure rate of 18 (low pressure of 0.1 MPa and high pressure of about 1.8 MPa). The designed mass flow is more than 14.8 mg/s. The preliminary experiment is carried out. A two-stage precooler capable of providing a pre-cooling capacity of about 15 K is used to verify the developed JT cryocooler. The test results show that the cryocooler successfully reached 4.5 K with a cooling power of more than 150 mW. A temperature fluctuation test is carried out. A long-term temperature fluctuation of more than 12 h has been tested. There exists a strong reaction among the temperatures of 4.5 K cold head, the precooling stages, and the ambient environment. The temperature fluctuation at 4.5 K cold head is within 5 mK/10 mins because of the large temperature fluctuation of the selected pre-cooler. The quantitative analysis of the temperature fluctuation of each temperature is discussed. By substituting the pre-cooler to a two-stage pulse tube cryocooler developed in our lab, the expected temperature fluctuation can be restrained to 1 mK@10 min and 5 mK@12 h, which can meet the requirement of future applications.

Improvement strategies for a low input power 4 K pulse tube cooler: Experiments and sage simulations

Optimizing the design of a two-stage Pulse Tube Cryocooler (PTC) usually affects its geometry and regenerator filling. Here, this is demonstrated based on a recently developed small scale two-stage PTC, driven by a 1 kW Helium compressor with an initial base temperature of 5 K. The improvements are aimed at reducing the minimum temperature and maximizing the cooling performance around 4.2 K. By rescaling the geometry, while keeping the overall length constant, and implementing Gd2O2S (GOS) in the regenerator filling, the coefficient of performance (COP) can be doubled from 7×10-5 to 1.5×10-4. The simulations generated with the software Sage agree with the experimental results and describe the cooling performance accurately down to 4.2 K. This demonstrates that such simulations are important to optimize PTCs around liquid Helium temperatures.

A two-stage thermally-coupled pulse tube cryocooler working at 35 K for space application

The attainment and maintenance of a low temperature environment is essential for aerospace cryogenic detectors to achieve their required performance. Developing cryocoolers with features of high efficiency, compact structure, and long lifetime is the main challenge for cryogenic detector cooling. In this paper, a high efficiency thermally-coupled two-stage Stirling type pulse tube cryocooler working at 35 K for HgCdTe long wave infrared detector cooling is designed and tested. The thermally-coupled type avoids gas distribution at cold side which minimizes the inter-stage influence. The whole cryocooler is driven by one linear compressor which enables compact structure. The influence of operation frequency and mean pressure is studied by numerical calculation and experiments to determine the optimum operation condition. Acoustic impedance characteristics of both stages and the whole cold finger are also analyzed by comparing performance of cryocooler with different frequency, mean pressure and structure dimensions. The distributions of acoustic power and phase angle are presented to study the relation between impedance characteristic and the cooling performance. Impedance match between compressor and cold finger is also discussed by analyzing the efficiency of the linear compressor and the performance of cryocooler with different pulse tubes. Under optimum impedance match and operation condition of a working frequency of 39.2 Hz and a mean pressure of 2.45 MPa, the cryocooler provides a cooling power of 1 W at 35.1 K with an input electrical power of 150 W, which indicates a relative Carnot efficiency of 5%. This is a rather high efficiency for developed Stirling type multi-stage pulse tube cryocooler working at 35 K with only inertance tubes as phase shifter. The development of this cryocooler lays a solid base for the further optimization to realize a competitive candidate for aerospace cooling requirements.

Cooling performance improvement of a two-stage pulse tube cryocooler with Er-plated screen as regenerator material

• A new regenerator material called Er-plated screen was proposed. • Comparision between Er-plated screen and stainless steel screen were involved. • Pre-cooling temperature, no-load temperature and cooling capacity were experimentally studied. • A lowest temperature of 15.29K with 235W input can be achieved while using Er-plated screen. As one of the key component in the pulse tube cryocooler (PTC), a regenerator needs to reduce losses for performance improvement. Thus, a good regenerator material should have large volumetric specific heat capacity and heat exchange area with small flow resistance. At present, high-mesh stainless steel screen and magnetic materials such as Er 3 Ni are commonly used as regenerator materials in the low temperature range. However, with the cooling temperature decreasing to lower than about 20K, the volumetric specific heat capacity of stainless steel decreases significantly, increasing the irreversible heat transfer losses of the regenerator. This paper proposes a new regenerator material which coats a magnetic material (Er) with high volumetric heat capacity at low temperature on the surface of stainless steel screen. The two-stage Stirling type pulse tube cryocooler (SPTC) with Er-plated screen filled in the cold end of the second-stage regenerator is investigated. The cooling performance of the SPTC filling with stainless steel screen and Er-plated screen is compared numerically and experimentally. A no-load temperature of 14.95 K can be obtained with an electric power of W when Er-plated screen is used. The relative Carnot efficiency (rCOP) of the cryocooler with Er-plated screen at 20K is 3.32 %, which is higher than with stainless steel screen. Another interesting phenomenon found in the research is that the rCOP of the SPTC with Er-plated screen reverses to be lower than with stainless steel screen when the temperature exceeds 30 K.

Numerical analysis of double inlet two-stage inertance pulse tube cryocooler

Numerical analysis of double inlet two-stage inertance pulse tube cryocooler

Low input power 4 K pulse tube cryocooler driven by an inverter helium compressor: Intrinsic temperature oscillations and mechanical vibrations

We report on the intrinsic mechanical vibrations and thermal oscillations of a small-scale two-stage pulse tube cryocooler operated by an inverter driven helium compressor. The combination offers a cooling power ranging from 35 to 156 mW at 4.0 K with an electric input power of 0.9 to 2.3 kW respectively. This system has been characterized with respect to mechanical and temperature stability. The acquired data from an accelerometer attached to the 2nd stage of the cryocooler shows a longitudinal peak-to-peak displacement of a few tens of μm. Additionally, temperature oscillations of a few hundred mK were found, with a maximum around 10.5 K. Based on this characterization, this article presents the reduction of these unwanted intrinsic effects by use of a compressor with variable operation modes.

30 K to 2 K vibration free remote cooling systems

Absolut System has built a 30 K and a 10 K remote Helium cooling loops used as a vibration free cooling source, respectively for IR detectors electro-optical characterization test bench and two-stage optical cryostat. The circulation loops are based on a by-passed flowrate from either a two-stage Gifford–McMahon cryocooler or a two-stage Pulse Tube cryocooler. Dedicated compact and high efficiency tubes & shell heat exchangers have been designed and produced for the recuperators. The paper describes the design and the performances of the vibration free cooling system produced. The current work towards a 4 K low vibration cooling source will be introduced as well.

A 15K two-stage gas-coupled Stirling-type pulse tube cryocooler

A gas-coupled two-stage Stirling-type coaxial pulse tube cryocooler (SPTC) driven by a dual opposed-piston configuration linear compressor was designed and experimental test. Both of the two stages adopted coaxial structure for compactness. At the cold end of first stage, a part of working gas was introduced to the regenerator of second stage, while the others were returned to the pulse tube of the first stage. A lowest temperature of 7.3 K and 0.3 W/15 K cooling capacity can be achieved with 250 W PV power by simulation. At present, a lowest temperature of 8.1 K and 0.56 W/15 K cooling capacity can be achieved with 600 W the input power. The influence of the frequency, amplitude of the positon and the hot end temperature were studied. This paper presents the simulation results and primary test results of the designed cryocoolers.

Investigation on numerical optimization method for high capacity two-stage 4 K pulse tube cryocooler

Two-stage 4 K pulse tube cryocooler is one of the most promising coolers for low temperature applications. However, an efficient and reliable method is still absent for pulse tube optimization in liquid helium temperatures due to complex heat and mass flow oscillation. In this study, a two-stage pulse tube cryocooler model was built with a commercially-available software, SAGE®. The DC flow effect on the performance was investigated and the filling ratio of second stage regenerator were numerically optimized. With the model, a no-load temperature of 2.7 K and a cooling capacity of 0.5 W at 4.2 K were achieved, which is well-matched with the experimental results.

Experimental research on the J-T orifice of a space 4.5 K hybrid J-T cooler

Hybrid J-T cryocooler is commonly employed in space detective missions requiring liquid helium temperature. In fact, nearly all the space applications of mechanical cryocoolers working at 4.5 K, having been launched or under development are hybrid J-T cryocoolers. For instance, mechanical cryocoolers used in Planck, JWST, SMILES, SPICA and so on, are all hybrid J-T cryocoolers. However, there is hardly any research on space 4.5 K hybrid J-T cryocooler in China. Key laboratory of space energy conversion technologies in Technical Institute of Physics and Chemistry (TIPC), Chinese Academy of Sciences (CAS) has developed a 4.5 K J-T cooler precooled by two-stage pulse tube cryocooler. Base on this cryocooler, the influence of supply pressure and diameter of the J-T orifice on the cooling capacity of the J-T cooler is analyzed and experimentally studied. First of all, the influence of supply pressure and diameter of the J-T orifice is theoretically calculated. Then, experimental research is carried out. For the purpose of shortening experimental time, a two-stage GM cooler instead of pulse tube cooler is used to precool the J-T cycle. Firstly, open loop experiments are conducted because it’s much easier to adjust the supply pressure precisely. The mass flow rate of the J-T cooler rises monotonously as diameter of the J-T orifice decreases. However, the cooling capacity of the J-T cooler goes through an up and down process because the J-T effect turns to be worse when diameter of the J-T orifice increases. That is to say, performance of the J-T cooler turns to be worse when the diameter of the J-T orifice is larger than 34 μm. Based on the research of this paper, 34 μm J-T orifice may be the best choice of the hybrid J-T cooler. Besides, both mass flow rate and cooling power increase as supply pressure increases when supply pressure is below 2.0 MPa. In addition, the no load temperature of the J-T cooler rises with increasing supply pressure which is attributed to the flow resistance of the counter-flow heat exchangers. Secondly, three-stage oil-free linear J-T compressors are used to drive the J-T cooler, and the suction pressure and supply pressure of the three-stage compression system are 0.12 and 2.0 MPa, respectively. Finally, cooling power of 81.5 mW @4.48 K is achieved when the total power consumption of the J-T compressors is 102.7 W. And the temperature fluctuation at the evaporator is lower than ±0.05 K because the cooling capacity of the J-T cooler is provided by the vaporization of liquid helium.

The study on a gas-coupled two-stage stirling-type pulse tube cryocooler

A two-stage gas-coupled Stirling-type pulse tube cryocooler (SPTC) driven by a linear dual-opposed compressor has been designed, manufactured and tested. Both of the stages adopted coaxial structure for compactness. The effect of a cold double-inlet at the second stage on the cooling performance was investigated. The test results show that the cold double-inlet will help to achieve a lower cooling temperature, but it is not conducive to achieving a higher cooling capacity. At present, without the cold double-inlet, the second stage has achieved a no-load temperature of 11.28 K and a cooling capacity of 620 mW/20 K with an input electric power of 450 W. With the cold double-inlet, the no-load temperature is lowered to 9.4 K, but the cooling capacity is reduced to 400 mW/20 K. The structure of the developed cryocooler and the influences of charge pressure, operating frequency and hot end temperature will also be introduced in this paper.

Numerical study of a gas coupled VM-PT hybrid cryocooler using 3He as the working fluid

The two-stage Vuilleumier gas-coupling pulse tube cryocooler (VM-PT) is one kind of novel low-frequency cryocoolers. In this gas-coupled form, the single stage Vuilleumier cryocooler serves as both pressure wave generator and a pre-cooler for coaxial pulse tube. Compared with the most commercialized GM and GM pulse tube cryocooler, the two-stage VM-PT cryocooler is characterized by its high stability, compact size and thermal actuation which are indispensable for space application. It has already been verified experimentally that this cryocooler can obtain 9.75mW@4.2K and the lowest no-load temperature 3.39K when 4He as the working fluid. However, such refrigerating capacity seems not enough for further application. 3He as a more potential substitution of 4He has better physical properties to improve performance, which has been studied in GM type and Stirling pulse tube cryocooler. For further optimization, a numerical study on the specific performance of two-stage VM-PT cryocooler using 3He is carried out in the present paper though Sage software. Working at the frequency of 1.0Hz and the pressure of 0.8MPa, the two-stage VM-PT cryocooler with 3He obtained 50mW@4.06K. The usage of 3He was 0.0038kg, about 30L under STP. At 4.2K, using 3He can obtain 58mW cooling power and 0.49% relative Carnot efficiency, about 1.6 times higher than using 4He.

A small two-stage pulse tube cryocooler operating at liquid Helium temperatures with an input power of 1 kW

The development of 4K two-stage pulse tube cryocoolers (PTCs) is commonly aimed at high cooling powers in order to compete with GM-cryocoolers. However, more sensitive applications still suffer from intrinsic disturbances of the cryocooler. To address this issue, the development of PTCs with small cooling powers is essential for sensitive measurements.Here we report the development of a new two-stage GM-type PTC, designed to work with a commercial Helium compressor with only 1kW electric input power. The pressure and mass flow oscillation is generated by means of a remote rotary valve. The PTC was modeled for the operation at temperatures near 5K with the simulation environments SAGE and REGEN. A first prototype was fabricated, operated and optimized in a test cryostat. Up to now, the PTC reaches a minimum temperature of 2.36K and provides a cooling power of 72mW at 4.2K and 120mW at 5K. This cooling power is sufficient for small cryoelectronic devices like single photon detectors, transition-edge bolometers or low-noise Nb-SQUIDs (superconducting quantum interference devices).